International Journal of Science, Engineering and Technologies (IJSET), vol.1, no. 3, Sept. 2013 @IRISET 2013 1 Abstract— As the world is heading towards paperless communication and transaction, the correct and authentic personal recognition is important to ensure that only legitimate users have access to the rendered services or information. Automatic recognition of individuals on the basis of their physiological or behavioral characteristics known as Biometric recognition or biometrics is now frequently used by service providers to authenticate personal recognition. Biometrics makes it possible to recognize the person on the basis of what he has (characteristics) rather than what he possesses (Id cards etc.) This paper provides an insight into various biometric characteristics their advantages, disadvantages, limitations and strengths. A systematic review of literature is carried out to identify future areas of research. Keywords— Biometric recognition, Iris, Retina, Unimodal systems. I. INTRODUCTION T is a common practice in our day to day life to identify a person on the basis of voice, walking, standing and gesticulation styles. We are able to recognize a person even when the person may not be visible to us clearly. Biometrics refers to the recognition of humans by their characteristics or traits called as biometric identifiers. Biometric identifiers may be classified into physiological characteristics/ identifiers and behavioral characteristics/identifiers. Physiological characteristics are related to the shape of the body. Examples include, but are not limited to fingerprint, face recognition, DNA, Palm print, hand geometry, iris recognition, retina and odor/scent. Behavioral characteristics are related to the behavior of a person, including but not limited to: typing rhythm, gait, and voice. As such, many different aspects of human physiology, chemistry or behavior can be used for biometric authentication. The selection of a particular biometric for use in a specific application involves a weighting of several factors. Jain et al. (1999) identified seven such factors to be used when assessing the suitability of any trait for use in biometric authentication. Universality: Characteristic should have universal presence i.e. each person in the population should have the characteristic. Er. Kanika Sharma is M.Tech scholar of Amritsar College of Engineering and Technology, Amritsar, Punjab, INDIA (kanikasharma2688@yahoo.com). Dr. V. K. Banga is working as a Principal and Head ECE of Amritsar College of Engineering and Technology, Amritsar, Punjab, INDIA. (vijaykumar.banga@gmail.com ). • Distinctiveness: no two persons should exhibit similarity in terms of the characteristic. • Permanence: the characteristic should be sufficiently invariant or stable (with respect to the matching criterion) over a period of time. • Collectability: the characteristic can be measured quantitatively. There are a number of other issues that should be considered in a practical biometric system (i.e., a system that employs biometrics for personal recognition), including: •Performance: refers to the achievable recognition accuracy and speed, the resources required to achieve the desired recognition accuracy and speed, as well as the operational and environmental factors that affect the accuracy and speed; •Acceptability: indicates the extent to which people are willing to accept the use of a particular biometric identifier (characteristic) in their daily lives; •Circumvention: reflects how easily the system can be hoodwinked using fraudulent methods. A biometric system is comprises of the following four main modules (see Fig. 1). 1) Sensor module: This captures the biometric data of an individual. An example is a fingerprint sensor that images the ridge and valley structure of a user’s finger. 2) Feature extraction module: This involves processing of biometric data for extracting a set of salient or distinguishable features. For example, the position and orientation of minutiae points (local ridge and valley singularities) in a fingerprint image are extracted in the feature extraction module of a fingerprint-based biometric system. 3) Matcher module: This involves the process of recognizing the features extracted and comparing against the stored templates to generate matching scores. For example, in the matching module of a fingerprint-based biometric system, the number of matching minutiae between the input and the template fingerprint images is determined and a matching score is reported. The matcher module also encapsulates a decision making module, in which a user’s claimed identity is confirmed (verification) or a user’s identity is established (identification) based on the matching score. 4) System database module: which is used by the biometric system to store the biometric templates of the enrolled users. The enrollment module is responsible for enrolling individuals into the biometric system database. During the enrollment phase, the biometric characteristic of an individual is first scanned by a biometric reader to produce a Biometric Security Issues: A Review Er. Kanika Sharma and Dr. V. K. Banga I